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Because an option grants the holder a right, it has value
for the holder. It represents a liability for the issuer.
Option valuation
is any procedure for assigning a
market value to an option.
This is especially important when an option is issued, since the issuer
will want to charge a reasonable price—what is called the
premium—for the option.
An option's expiration value
is its market value at expiration. In the case of a
call, expiration value
(per unit of notional amount) is
either:
zero, or
the difference between the value of the
underlier and the
strike
price,
whichever is greater.
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This exhibit illustrates how the
expiration value of a call option (per unit of notional amount)
varies with the value of the underlier at expiration. If, at
expiration, the underlier value is below the strike price, the
option expires worthless. Otherwise, its expiration value is the
value of the underlier less the strike price. |
Consider a call option on 200 ounces of gold struck at
USD 375. If the market price of gold is USD
400 when the option expires, then
the call's USD expiration value will be:
200 max( 0 , 400 – 375 ) = 5000.
This reflects the fact that the option holder can exercise
the option to purchase 200 ounces of gold for USD 375 per ounce, and then
immediately sell the 200 ounces at the market price of gold, which is USD
400 per ounce.
Suppose instead that the price of gold were USD 360 when
the option expired. In this case, it would make no sense for the option
holder to pay USD 375 for gold when the market price is only USD 360. The
option holder would not exercise the option, and it would expire
worthless. Its market value at expiration would be:
200 max( 0 , 360 – 375 ) = 0.
In the case of a put, its expiration value (per unit of
notional amount) is either:
zero, or
the difference between the strike price and the current
value of the underlier,
whichever is greater.
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For each unit of notional amount, the
market value of a put option at expiration is equal to either zero
or the difference between the strike price and the underlier value,
whichever is greater. |
Consider a put option on 200 ounces of gold struck at USD
400. If the market price of gold is USD 380 when the option expires, then
the put's USD expiration value will be:
200 max( 0 , 400 – 380 ) = 4000.
This reflects the fact that the option holder can purchase
gold at the market price of USD 380 and then exercise the put, selling the
same gold for USD 400.
Option valuation is more complicated prior to an option's
expiration. A useful notion is that of
intrinsic value, which is simply what the option's value would be
if the option were about to expire. Prior to expiration, an option's
market value will generally exceed its intrinsic value by an amount that
is called the option's time value.
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Prior to expiration, the market value of
an option comprises two components: intrinsic value and time value.
This is illustrated for a call option. |
For example, consider a call option on gold that is struck
at USD 400 and will expire in three months. If the current price of gold
is USD 390, is the option worthless? Would you be willing to give this
option away for free? Certainly not! The option has no intrinsic value,
but three months remain until it expires, and the price of gold may rise
during that time. The option has time value.
An option is said to be
at-the-money if the underlier value currently equals the strike
price. Otherwise, the option is said to be
in-the-money if it has positive intrinsic value, or
out-of-the-money if it has zero
intrinsic value. A call is in-the-money if the underlier value is above
the strike price. A put is in-the-money if the underlier value is below
the strike price.
While intrinsic value is easy to calculate, time value is
more difficult to calculate. Historically, this made it difficult to value
options prior to their expiration. Various option pricing methodologies
were proposed, but the problem wasn't solved until the emergence of
Black-Scholes theory in 1973.
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dynamic
hedging A technique that is widely used by derivatives dealers
to hedge gamma or vega exposures.
Greeks A set of
factor sensitivities used to measure risk exposures related to
options or other derivatives.
option
A type of derivative instrument.
option pricing theory The
body of financial theory used by financial engineers to value options and other
derivative instruments.
option
spreads
Positions combining one or more options in a single underlier.
put-call
parity
A formula that relates the price of a put to the price of a
corresponding call.
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Kolb (2002)
is a practical introduction to derivatives. Cox and Rubinstein (1985)
is a classic. Pretty much everyone who works with options has read
it at some point. Natenberg (1994)
is an excellent introduction to options trading. Read Baird (1993)
after you read Natenberg.
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